How to convert CentOS root file system to XFS

Jephe Wu -

As you know, the CentOS is a clone of Redhat Enterprise Linux. CentOS doesn't support XFS file system by default which is the same as RHEL, but CentOS provides additional kernel which has built-in XFS support. You can download it to replace the existing kernel to easily get XFS support in kernel space. But the problem is how to make your /, /usr,/var etc partition as XFS file system since you already used ext3 during installation.

This article is to guide you to do that, the following is my testing environments:

CentOS 4.1
/dev/hda1 -/boot (ext3)
/dev/hda2 - swap
/dev/hda3 - / (ext3)
/dev/hda5 - /usr (ext3)
/dev/hda6 -/var (ext3)
/dev/hda7 - /tmp (ext3)
/dev/hda8 - /serverdata (ext3)(for storing data later, it's empty after installation)

Our objective:
convert all partitions except for /boot from default file system ext3 to XFS. Grub doesn't support XFS so we leave /boot as ext3.

Clone and XFS convert concept:
a. download XFS-enabled kernel from CentOS and install it
b. use /serverdata partition to save all server OS partitions such as /boot, /,/usr,/var,/tmp
c. boot up server using RIP(Recovery Is Possible) CD
d. format all partitions as XFS
e. copy back all data from /serverdata
f. change /etc/fstab and /boot/initrd image file
g. done. reboot


a. download the latest RIP CD at
download Non-X version is enough

b. download the XFS enabled supported kernel from CentOS website and install it to the server
# rpm -ivh xfs-enabled-kernel
# vi /etc/grub.conf
to make sure it will boot with the new kernel next time
# reboot
(make sure it can boot normally with new kernel)

c. copy the whole server OS to /serverdata, make xfs file system then copy back
c.1 reboot server with RIP CD after upgrading to xfs enabled kernel, you might want to choose the second option to skip keyboard map
c.2 login as root without password
c.3 make /serverdata partition as XFS first and backup the whole OS to /serverdata
mkfs -t xfs /dev/hda8
cd /mnt
mount /dev/hda3 hd
cd hd
mount /dev/hda1 boot
mount /dev/hda5 usr
mount /dev/hda6 var
mount /dev/hda7 tmp
mount /dev/hda8 serverdata
chroot .
tar --exclude ./boot --exclude ./proc --exclude ./serverdata -cpf - .| (cd serverdata; tar xvpf -)

c.4 umount all partitions then make xfs file systems
exit (exit from chroot environement)
cd /mnt/hd
umount usr
umount var
umount tmp
umount serverdata
umount boot
cd ..
umount hd

mkfs -t xfs -L / /dev/hda3
mkfs -t xfs -L /usr /dev/hda5
mkfs -t xfs -L /var /dev/hda6
mkfs -t xfs -L /tmp /dev/hda7
note: -L to make label for partition, be sure to use the same label name in /etc/fstab.

c.5 mount them again like c.3
cd /mnt
mount /dev/hda3 hd
cd hd
mount /dev/hda1 boot
mount /dev/hda5 usr
mount /dev/hda6 var
mount /dev/hda7 tmp
mount /dev/hda8 serverdata

c.6 copy back the whole OS from backup
(cd serverdata; tar cpf - . ) | tar xvpf -

d. make necessary changes
d.1 change /etc/fstab
cd /mnt/hd
chroot .
vi /etc/fstab (to change file system for those changed from ext3 to xfs, if you didn't use -L option in above mkfs -t xfs for /, /usr,/var,/tmp partitions, you also need to change the LABEL= to the real device name like from LABEL=/usr to /dev/hda5)

d.2 change /boot/initrd image file
cd /mnt/hd
chroot .
cp /boot/initrd.img /tmp/a (use the correct name for your initrd image, I use /boot/initrd.img here)
cd /tmp

zcat a > a1

mkdir a1.dir

cd a1.dir

cpio -iv < ../a1

modify something

vi init ( change ext3 to xfs, add xfs.ko module in init as well as lib/ folder) as follows:
[root@linuxtechres ]# more init
mount -t proc /proc /proc
echo Mounted /proc filesystem
echo Mounting sysfs
mount -t sysfs none /sys
echo Creating /dev
mount -o mode=0755 -t tmpfs none /dev
mknod /dev/console c 5 1
mknod /dev/null c 1 3
mknod /dev/zero c 1 5
mknod /dev/hda3 b 3 3 ---> added, hda3 is the root file system device
mkdir /dev/pts
mkdir /dev/shm
echo Starting udev
echo -n "/sbin/hotplug" > /proc/sys/kernel/hotplug
echo "Loading jbd.ko module"
insmod /lib/jbd.ko
echo "Loading ext3.ko module"
insmod /lib/ext3.ko
echo "Loading xfs.ko module"

insmod /lib/xfs.ko ---> added - please remember to copy xfs.ko file from /lib/modules/kernel_version/kernel/fs/xfs/xfs.ko to /lib
echo Creating root device
mkrootdev /dev/root
umount /sys
echo Mounting root filesystem
mount -o defaults --ro -t xfs /dev/root /sysroot ---> change ext3 to xfs
mount -t tmpfs --bind /dev /sysroot/dev
echo Switching to new root
switchroot /sysroot
umount /initrd/dev
re-generate initrd.img with xfs support
find . | cpio -co > ../c
cd ..
gzip c
cp c.gz /boot/initrd.xfs.img
change /etc/grub.conf to use this new initrd.xfs.img file.
d.3 install grub
cd /mnt/hd
chroot .
grub-install /dev/hda
After that, umount all partitions, reboot the server.